Logical Characteristics; Scsi-Bus Phases; Bus Management Phases - Tandberg Data SLR7-140 PROGRAMMER Manual

3.

Logical Characteristics

3.1.

SCSI-bus Phases

The Drive implements the following SCSI-bus phases:

Bus management phases

BUS FREE
ARBITRATION
SELECTION
RESELECTION
Table 3-1:
The SCSI-bus will never be allowed to be in more than
one phase at any given time. See also [2], [5] and [6].
See also [1] for timing diagrams showing SCSI-bus signal
activity.
3.1.1. Bus Management Phases
3.1.1.1. Bus Free Phase
The BUS FREE phase is used to indicate that no SCSI
device is actively using the SCSI-bus and that it is
available for subsequent users.
The Drive enters the BUS FREE phase by releasing BSY
after one of the following conditions:
after a SCSI-bus RESET condition
after an ABORT message has been received
after a BUS DEVICE RESET message has been received
after a DISCONNECT message has been transmitted
after a COMMAND COMPLETE message has been transmitted
after certain SCSI protocol errors (see section 6.6
Unexpected Bus Free )
The Drive enters the BUS FREE phase by releasing SEL
after the following condition:
after an unsuccessful reselection of an Initiator
3.1.1.2. Arbitration Phase
The Arbitration phase allows the drive to gain control
of the SCSI-bus so that it can resume or initiate the
connection with an other device on the bus.
3-1 Tandberg SLR Product Line SCSI Functional Specifications
Information transfer phases
COMMAND
DATA-IN
DATA-OUT
STATUS
MESSAGE-IN
MESSAGE-OUT
SCSI-bus Phases